But the OP is looking specifically for 296/ 110 . Implied is that his two powder choices are 296 and Trail Boss .
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Super Cholo , those two powders are both specialized powders , at opposite ends of the spectrum . Trail Boss for light powder puff loads , and 296 for full house maximum loads . That's fine if that's what you are seeking on purpose . If you would wish something inbetween , you would need an additional powder . There are a plethora of powders with more flexibility , suitable for loads in medium range up to more or less equivalent to mainstream factory loads .
You expressed liking that Trail Boss for being " safe " . Presumably using the usual context of being difficult to inadvertently reaching unsafe pressures .
The 4227 mentioned by Ralph H above would be similar in that regard . In virtually any combination , a compressed charge of 4227 will still be safe in your .44 Magnum . Downloading will be " safe" with the caveat that as you reach the lower end ignition can get inconsistent .
My default starting point for magnum revolvers for a certain power level are : normal for caliber weight bullet ( yes , 240gr -ish for .44) , and 90% load density of 4227 . The worst accuracy that formula has given me is 1.25 inch @ 25yds .
The usual complaint about 4227 is being " dirty " . Meh . Clean the gun every couple hundred rounds anyway .
Maximum velocities with 4227 are a bit less than with the usual yardstick of 2400 . But still definitely Magnum class , and probably plenty fast enough for most any purpose to use a 240gr .44 .
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We don't know what other loads and powders you are experienced with , but I'll throw out some general discussion .
With heavy loads of slow powders as a class , the bullet resistance aka Case Neck Tension is important for proper powder burn , which effects accuracy , consistency , and reaching expected velocities .
This is a combined factor of bullet diameter , expanded neck inner diameter , and crimp . Average mainstream die set may well prove sufficient , but you need to be aware and check , instead of assuming .
If there are issues , there are multiple ways to deal with that . Including using .430 or even .431 projectiles instead of .429 , polishing down the case expander by 0.001 or 0.002 smaller diameter , or specialty crimp dies , or combinations thereof .